There are known in the prior art devices for counting currency. Many of these counters employ photodetectors which serve the dual purpose of providing a count as notes pass by the detectors and of affording an indication of double feeds as by overlapping bills. Many of these detectors incorporate manually adjustable potentiometers for calibrating the LED-photodiode pairs making up the photodetectors.
One of the difficulties with counters of the type known in the prior art is the necessity for manually calibrating the LED-photodiode pairs.
While the doubles detection of counters of the prior art is generally satisfactory, it is not as certain as is desirable owing to dirt or dust in the optical system, for example. In doubles detection systems of the prior art an error signal is sounded and the machine is stopped each time a double is detected. Consequently such a doubles error requires that the operator restart the operation. By "double" we mean the delivery of two sheets at a time to the feed path or overlapping sheets.
Many of the counterfeit detectors of the prior art are provided with a magnetic means for detecting the presence of counterfeits. While these counterfeit detectors are in some degree satisfactory, they require readjustment for differences in component characteristics from unit to unit, magnetic ink or for different denominations or from batch to batch.
Machines of the prior art are capable of a slow speed batching operation which is employed by the operator in order to observe each note as it moves into the output tray. Such an operation might be used, for example, to detect the presence of a five dollar note among a stack of one dollar notes. In machines of the prior art the possibility exists that upon a slow speed hatching operation, the last bill of the batch which has been moved into the feed path and counted may never reach the output tray.
Some machines of the prior art may be set to count a predetermined number of notes per minute. When the length of the documents being counted changes, the count number per unit time is no longer accurate. By "length" we mean the dimension of the document in the direction of feed.
Certain machines of the prior art are in some degree programmable. However, the preset program is lost in the event of an interruption of power.